US President Donald Trump has called on Syria and Russia to halt air strikes on Syria’s Idlib province, the last stronghold of opposition to President Bashar Al Assad, which is home to around three million civilians. "Hearing word that Russia, Syria and, to a lesser extent, Iran, are bombing the hell out of Idlib Province in Syria, and indiscriminately killing many innocent civilians. The World is watching this butchery. What is the purpose, what will it get you? STOP!" Mr Trump wrote in a Twitter post. Idlib in north-west Syria is the last bastion of territory held by Islamist militants and armed opposition groups, which the government is coming ever closer to routing after a series of peaceful anti-government protests in 2011 morphed into a full-blown internal conflict. In 2015, Russia said it was entering the Syrian war to quash terrorist groups like ISIS that have risen to prominence amid the conflict. The Kremlin’s brutish air campaign, which mostly targeted moderated opposition groups, turned the tide of the conflict in favour of Syria’s embattled president who was losing swathes of territory. Mr Assad and his Russian allies have been eager to launch a final and conclusive assault on Idlib, a battle that would ostensibly see the regime regain full territorial control of the country. However, the leaders of Russia, Turkey and Iran agreed in September to pause hostilities, handing over responsibility for reeling in opposition groups to Ankara. Turkish officials are worried that a full-scale assault on Idlib will send a massive wave of refugees fleeing the conflict towards its borders. Turkey already hosts more than three and a half million Syrians who have fled the conflict. However, Russia is running out of patience with Turkey’s efforts to keep Hayat Tahrir Al Sham, the dominant Islamist group there, and other opposition groups in check. Officials in Moscow last month accused rebels in Idlib of launching drone and rocket attacks on Russia’s airbase in Latakia. In response to Mr Trump’s tweet on Monday, Kremlin spokesperson Dmitry Peskov reiterated the claim, saying that the regime’s month-long assault on the province was necessary for the battle against extremism in the country. "In Idlib, there is still a fairly high concentration of terrorists and militants who use this to attack – both at civilian targets and (for) various aggressive attacks towards Russian military targets, such a situation is unacceptable," Mr Peskov said, adding Turkey was ultimately responsible for ensuring that such attacks do not happen. In a sign of growing tensions over Idlib, Turkish President Tayyip Erdogan has accused Mr Putin and the Assad regime of indiscriminately bombing civilian infrastructure including schools and medical facilities. Since Russia and the Syrian regime began its offensive north of Homs, some 200,000 people have fled the flighting, according to the United Nations. Doctors in Idlib told The Telegraph newspaper last week that Russia and the Syrian government air strikes had hit at least eight medical facilities in the province even though the coordinates of the hospitals and health centres had been shared with Moscow and Damascus in advance.